RD350 7 plate clutch question

[soonerbillz]

So I bought this complete "late" RD350 clutch pack the other day.
I've read Supertune's write up on the swap from the R5 setup to this 7 plate unit several times trying to make certain I have all the correct parts.
While inspecting the new to me RD clutch parts I've noticed something odd. On the RD clutch I received the inner boss part is indeed bolted together vs being a one piece cast part like my R5 has. The thing I noticed when comparing the RD part I have against pics from Supertunes's post and pics I've found on the web of other RD inner boss's is the actual bolt holes and subsequent threading. Supertune's RD inner boss and all the online pics show an enlarged cast area where the bolt goes into, where the bolt hole was drilled and tapped.
On my new RD inner boss the part where the bolt hole was drilled and tapped does not have this enlarged casting and the drilling process "broke" through the casting into the web.
This seems odd and not in a good way.
Anyone ever seen this before?

[soonerbillz]

These are pics from Supertune's post. I enlarged it to show the area I'm talking about

[soonerbillz]

These are pics of my RD inner boss

[Jspooner]

I'm wondering if someone modified a six plate inner boss to make it like a 7 plate inner boss?

[soonerbillz]

I'm wondering if someone modified a six plate inner boss to make it like a 7 plate inner boss?

Why in god would anyone do that ?
I'm totally confused by this. 

[m in sc]

or somebody just changed the bolts and retapped. if its the right size id roll with it.

[rdsarefun]

I sold the parts to this gentlemen and pulled these from a 75 RD350 bottom end, can't vouch for the authenticity as I did not own since new, bought in a "lot" of bikes/parts with a bottom end and a serial number indicating from a 75.  I have seen the pics and do realize that a difference exists, with extra webbing around the bolt holes but have no idea if different manufacturing locations or suppliers have different castings, was just asked to provide the parts for a 6 speed upgrade which I did.  In my line of business, we have many parts suppliers that sell to us where the function is the same (fit and purpose) but parts are manufactured look somewhat different externally.  I have no idea if Yamaha manufacturers everything or outsources this, never crossed my mind.  I have another clutch boss at home, will look at this and see if it is the same.  Thanks, Brian

[soonerbillz]

Brian... not calling you out on this.. I'm just confused.
I've spent the last 2 days trying to find a pic of another similar version and could not.  All the ones I'm seeing have the casting like in the 1st pic.
I was posting here to find out what was what.. not to blame or accuse of funny stuff.  I do appreciate all your efforts to help me.

[rdsarefun]

No worries, this never crossed my mind as I just removed, cleansed and bagged and tagged for future use.  I am also interested in determining what is going on, is it a swapped unit or from another supplier/vendor if Yamaha outsourced.  I looked at EBay and have seen some different hubs.  One that has the webbing per Chuck's pics, one that has thicker ribs and no additional "meat" left or right of the tapped hole (where the thread and hardware is not exposed) and this one.  Interesting is the pic of the threaded web having a flat bottom, as if milled and not drilled as the "lead in" would be pointed.  Additionally a standard tap was used when threading as the thread form does not go the whole way to the bottom of the hole, only enough to have clearance for bolt used.  Manufacturing this would require a tool change and a bottom tap, costing time and money put into a part if this was not modified and factory or supplier dependent.  Regardless, I will look at my clutch I have at home and get back to you